Opuntias are probably the best known of all the different cacti genera and are more commonly known as prickly pears. The group has, in fact, been divided into more than ten genera and has been known to scientific literature since earliest times. The name opuntia derives from the supposed locality in Greece where it was first seen, but opuntias. although seen in great quantities all round the Mediterranean, are not native to that part of the world at all, and like all other cacti originated in the
Opuntias also have the distinction of having claimed Goethe's attention: he raised some from seed and made a considerable study of the plant, particularly of the cotyledon leaves, and embellished his notes with concise and accurate illustra-
The name prickly pear derives from the use of the fruits as food. In order to remove the spines the fruits are roasted, and the skin together with the spines is then peeled off leaving the flesh exposed, something
Scientifically the genus is divided into quite a large number of subgenera but for the purposes of this book I propose to divide them into two groups: those that form fleshy pads, like the ones most commonly associated with the name, and those that are upright and cylindrical and which could easily be mistaken for some other type of cactus. The most important feature of opuntias which enables scientists and others to place them immediately is the presence of glochids. These are small bristles which detach themselves very readily from the areoles and can pierce the
Great care should, therefore, be exercised when handling the plants. If you do get some of these bristles in your lingers the best way to get rid of them is with one of the rubbery sorts of glue. This should be smeared over the affected area and then when it has hardened and become elastic it should be pulled off and the spines should come away with it. If there is no glue available soap and water can help.
Propagation is very easy and the pads root readily when detached and plunged in a mixture of peat and sand. Before attempting to root them it is best to cut off the bottom quarter of an inch (6 mm) in order to provide a larger area from which the roots can develop.
The two species illustrated are both quite distinctive. Brusilupuntiu brasiUensis is a very attractive kind with small pads. The pads are of two different sorts, those nearest the main stem are circular but as they get further from the stem they become increasingly oblong or elliptical. The flowers are white but they are seldom produced on smaller plants, which grow fairly slowly.
Opunlia basilar is is commonly known as the beavertail cactus on account of the shape of the pads. It is not so commonly seen as the preceding species and is slightly delicate. It is particularly susceptible to fungal attacks during the autumn and winter and it is advisable to drench the plants before their winter rest with a sys-
It will probably also benefit from being kept slightly warmer during the winter if possible as this will help to keep the roots active and able to resist any attack. The thick joints are almost grey in colour but are tinged reddish round the edges. It is frequently spineless although there is the usual proliferation of yellowish-brown glochids in the recessed areoles. The flowers, like those of B. brasiUensis, are only produced on older plants and since this species is extremely slow growing flowering cannot be reliably expected on pot-grown specimens.
Opuntia bergeriana and O.rafinsequei are the two species most commonly seen round the Mediterranean and both of them have edible fruits. They are semi-hardy and will do well if planted out in a conservatory. O. bergeriana ultimately becomes a large tree-like plant and will eventually have spreading branches and occupy a lot of space. In order to encourage rapid growth and to enable the plant to reach the considerable size necessary for it to flower profusely it is best to plant it out in the ground if this is feasible. If this is not possible, it should be fed heavily during the summer months to encourage it to develop to the maximum size in the smallest possible pot without starving it unduly. When grown in pots, and as soon as they attain some size, these plants make very attractive additions to a patio or they can be spread round a swimming pool during the summer when the fresh air circulating through the branches will help to ripen the stems sufficiently to produce flowers the following
Opuntia bergeriana will ultimately develop a sizeable trunk and tends to become somewhat unsightly as the trunk is inevitably brown and appears to be pockmarked with woody-coloured scars. At first the pads are a refreshing pale green colour but as they age they gradually assume a bluish frosting. The spines are slightly bent over at the tip and in older specimens can grow up to 2 in (5 cm) in length. The flowers, when they are eventually produced, are profuse and orange in colour with a central green six-lobed stigma.
Opuntia engelmannii is almost the exact opposite of the preceding species and tends to sprawl around, branching freely so that it has a semi-prostrate habit although, of course, younger specimens in pots will have the usual upright appearance. For this reason it is best to let the plant graduate to a more saucer-shaped bowl or pot rather than restricting it to a conventional pot. or. best of all. to plant it out if possible in order to allow it to reach its full size and the shape which is characteristic to it. The joints are very thick and can be up to a foot (30cm) in diameter in mature specimens: they tend to appear a little starved in colour but this is their natural appearance. As with O. bergeriana, the flowers are only produced on well established mature specimens, and planting out the cactus will enable it to reach flowering size more rapidly. The areoles are extremely pronounced. bulging conspicuously outwards from the surface of the pads, and like most opuntias they are filled with dirty looking greyish wool. The flowers are yellow on the outside and red on the inside and are up to 4 in (10 cm) in diameter. O. engelmannii is not really to be recommended to anyone who is either just starting a collection or who has only a small amount of space as it is neither particularly ornamental in itself nor characteristic of the mature plant while grown in a small pot.
Opuntiaficus-indica is the original prickly pear and has the finest of all fruits as far as edibility is concerned. The joints are elongated and up to 18 in (45 cm) in length and are much darker than either of the two pre ceding species. Like O. basilaris it is almost completely spineless and the areoles only have the usual whitish wool and straw-coloured bristles.
Nopalea coccinellifera is another very similar species which is useful as a host plant for the cochineal bug from which the food colouring is made. Like O.ficus-indicu it is almost spineless but it does not grow so tall and has red flowers as opposed to the yellow ones of O.ficus-indica.
Opuntia leucotricha makes one of the best pot plants of all the opuntias which are commonly sold in the shops. The dark green pads make an excellent contrast to the long wispy white hairs or bristles that grow out of the areoles and surround the oblong and can grow up to 7 in (18cm) in length. This species has the advantage of being comparatively fast growing but the attractive yellow flowers are only produced on mature plants. In its wild state it can attain a height of 15 ft (4-5 m) or more with numerous spreading branches. A curious feature is the aromatic pulp that is produced from the seed. The plant is sometimes sold under the name of Aaron's beard.
Two other species with white spines are O. amyclaea and O.spinulifera, but the spines are less closely packed together on the joints than in the illustrated species and they are much less commonly seen in cultivation. O.bella is distinguishable by its brown hairs and the much thicker and stronger spines (the spines of O. leucolriclui are very weak and can easily be broken or damaged in handling).
Opuntia microdasys as commercially available covers an extremely wide variety of forms with different shapes, sizes and colours. The three most commonly seen varieties are described here and on the next page. O. microdasys itself is frequently a low. creeping shrub in its native habitat but in cultivation it is normally upright, the prostrate habit, as with so many other natural phenomena, coming only with old age. The joints are either oblong or roughly round in shape, can grow a little over 5 in (13 cm) in length and are normally spineless. The absence of spines, however, should not be regarded as carte blanche to handle the plant without respect as. in common with all other species of Opuntia. it is the glochids round the base of the spine which detach themselves so easily when touched and adhere to the skin causing grave irritation. The species is commercially grown on account of its prominent closely set areoles which are densely packed with straw-coloured. yellow or brown glochids. Flowers can be produced on plants of six years of age or more and will ultimately be carried in great quantity; they are a magnificent pure yellow lightly suffused with red.
As mentioned earlier there are a great many variations on the basic species and one of the most commonly seen is O. m. albispina which is sold in the United States as polka dots, a name aptly describing its appearance. The joints are a very much darker green, more akin to O. leucotricha. and the glochids are pure white. There are some varieties of 0. m. albispina coming on the market now which lose their glochids less readily and there is also a variety labelled O.m.alba whose areoles are set slightly further apart.
The opuntias illustrated above and on the next page are particularly susceptible to a type of brown rust-coloured spotting which can be observed on the plants during the late winter or early spring. The discoloration is not in itself harmful and no sprays need be applied. Il appears to be caused by the plants being allowed to be come excessively cold and damp during the winter and the best way to prevent it is to grow them slightly warmer, if this is at all possible. In a greenhouse with limited possibilities for temperature differentials, the best idea is to place plants which are likely to be affected in this way nearer to the sources of heal with which the greenhouse is provided. Care musl be taken, on the other hand, not to allow the plants to become desiccated or shrivelled and the first signs of this occurring should be followed by watering the following morning.
Opuntiu microdasys rujida is very similar to both the preceding species but differs in the straw-coloured ones of O. microdasys and the white ones of O. m. albispina. The joints are paler green than in the preceding species and a little darker than those of the true species. In addition to the one illustrated there is a variety which is sometimes seen called O. m. rujida minor. This is probably not a true relative of O. microdasys as the joints are slightly cylindrical in shape instead of being flat, but it shares the spreading prostrate habit of the others. O. rujida is. on the other hand, a completely different species and is more erect than O. microdasys. As a plant this species grows to far greater size than O. microdasys and the joints are more rounded in shape and a more greyish green in colour. Rudimentary leaves are frequently produced, sometimes up to 2} in (6-5 cm) in length and often with a reddish tip. The flowers are yellow or orange but. as with most opuntias, are only produced on older plants. Although not commonly available it is a good grower.
Opuntiu monacantlia and O. vulgaris are frequently confused with one another and some authorities even consider that they are the same plant. To make the confusion worse the name O. vulgaris is frequently given to other opuntias. ranging from the upright O.Jicus-indica illustrated and discussed on page 102, to a low creeping species which is probably O.compressa, thus belying the botanists claim that Latin names do enable the purchaser to know exactly 104 what he is buying. The distinguishing feature of O. monacantlia is supposed to be its single spine but it is not uncommon for parts of the trunk of mature specimens to have ten or more spines and most joints normally have up to two sprouting from each areole. The plant is upright and can attain a height of 7 ft (2-25 m) or more in its native state. The joints are usually oblong in shape but can be more rounded so that they are almost oval, however, they always narrow markedly at the base. The skin is dark green and very glossy and the flowers, when produced, are bright yellow. The areoles are fairly distant from each other and the glochids are less troublesome than those of many other species and brownish in colour.
There is an interesting though somewhat delicate variety of O. monacantlia known as U. m. variegata. As its name implies this plant is variegated and the young growth is often suffused with pink. It is a very weak grower, however, and seldom reaches any great size in cultivation. The spines are much more brittle than in the true species.
Another species often confused with O.monacantha is Nopalea coccinellifera: this latter plant is. however, usually spineless. Both species are widely used in their native habitat as host plants for the cochineal bug from which the dye of the same
Opuntiapuberula is another species where considerable confusion exists over the exact species to which the name refers. The true O. puberula is a low. often creeping plant, which is seldom seen in cultivation to any cwnbens. The variety more -commonly offered as O. puberula should, in fact, be sold as O. x puberula. the cross indicating that it is not a species at all but a hybrid. The parentage of this variety is not known for certain but most authors seem agreed that it is a hybrid between the O. microdasys described earlier and O cantabrigiensis. The hybrid differs from O. microdasys in having more distantly spaced areoles, but it is much hardier and this it derives from its other parent which to this day can be found growing outside the glasshouses in the Cambridge Botanic Gardens.
Opunlia robusia is one of the largest jointed species available to the amateur and is as vigorous and upright as its name suggests. It develops many branches and the pads will ultimately grow to a foot (30cm) or more in diameter. They are also extremely thick and of a bluish-green shade. Although in its wild state the species usually produces between eight and twelve very stout spines varying in colour, even on the same plant, from a deep brown to a pale yellow, the specimens grown in greenhouses in pots are usually spineless. The plant will also not attain its full-size pads unless it is planted out in the soil. The flowers, which only appear on older specimens, are yellow, occasionally tinged red on the outside. The fruit is deep red in colour and this distinguishes it from a similar species called O. guerrtma which has greenish-white fruits and is not so commonly found in cultivation. O. robusia is very widely cultivated for
Opunlia spinosissinui is typical of another erect-growing group of prickly pears, which, however, may need staking when cultivated. The stems of this group of cacti are hardly jointed at all, and the pads appear to elongate with age rather than to make fresh ears. O. spinosissima is densely covered with areoles. which are in turn packed with brownish glochids and vicious spreading spines up to 3J in (9cm) in length. The body of the plant is a dull green, and because of the unusual growth habit of the plant the joints can be up to three times as long as they are wide. The flowers, which are produced only on mature specimens, arc at first yellow but turn red as they grow older.
Opunlia tuna is another plant which although it grows erect in its native state frequently needs some support in the greenhouse. It is a fast-growing variety and therefore ideal for the beginner or for someone with ample space at their disposal. It can attain a height of 12ft (3-5 m) and the dark green joints are elliptical in shape with large areoles from which two to four, or occasionally more, spines emerge. The glochids and spines are both yellow as are the flowers, which are produced only on adult specimens.
It is worth appending at this point a short note on the slaking of cacli. Slicks are not. of course, normally available to a plant in its natural state and the upright-growing varieties should not require sticks if grown properly in cultivation. Generally speaking if a plant starts to flop about and if both it and its roots have reached a fair size, it is probably better to pot it on to enable the roots to have greater access to and draw up sufficient food to support the plant in a vertical condition. If the plant has not got sufficient roots to justify potting on. then, except in cases where I specifically recommend staking, it is probable that there is something amiss with the plant and the best bet is probably to cut the plant back to some upright joints and allow it to start again and to grow up more strongly.
Before leaving this section on flat-jointed opuntias. I would also like to mention the phenomenon of cristation. This occurs naturally even in several English wild plants such as the thistle and normally indicates a thickening of the stem. In cacti, which are virtually all stem, this can cause convoluted shapes, which are of a generally crested appearance as the name implies. The growth of the plant is otherwise in no way inhibited and such plants arc often greatly prized by collectors. Occasionally a quite normal plant will throw out a cristate branch and when this occurs it is often a good idea to remove the affected section, making a clean cut with a knife, and then to graft it back on to Cereus stock, following the instructions given for grafting on page 97. There is a slightly similar form known as a monstrose variety, in which the plant retains its cylindrical appearance but loses its regular structure. Cristate varieties are normally indicated by the presence of the word 'crislala' after the name of the plant, and monstrose varieties by the addition of the word 'monstrosa'.
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